Input: mxs-lradc - do a NULL check on iores

platform_get_resource() may fail, so we should better do a NULL check
and return error on failure.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>